While testing AMD's A10-5800K APU, Xbitlabs.com discovered a rahter interesting thing that might be a real problem for AMD APUs as, at least some of them, might have a problem related to the TDP and downclocking.

According to Xbitlabs.com, their AMD A10-5800K sample was behaving rather strangely and in some screnarios dropped way below its 3.8GHz base clock. As you already know the A10-5800K has a base clock of 3.8GHz while it can turbo up to 4.2GHz.

While putting the APU under high multithreaded load, the clock speed ended up at 3.4GHz, which is way below the base 3.8GHz clock. The reason apparently lies in TDP as when it exceeds its default level, the APU drops its base clock. Xbitlabs.com noticed the problem in Linpack benchmark as well as in various video encoding apps and 3D renderers showing that the APU delivered lower performance than expected. Strangely enough, the drop does not happen when APU is forced to work without AMD Turbo Core, but the APU is then locked at 3.8GHz.

According to Xbitlabs.com, AMD is quite aware of the problem but notes that it occurs in very rare cases under loads that are not typical for client microprocessors, so an average user will not notice it.

It is not a big of a deal as benchmarking will definitely put much more strain on the APU or CPU than any average user will ever do and as soon as TDP drop below the treshold it should go up to at least its base clock.

We have been contacted by AMD's Public Relations Manager, Peter Amos, stating that the graceful clock throttling via the Turbo Core Technology when TDP is exceded by benchmarks in an unrealistic scenario is indeed a good design decision rather than issue. The original Xbitlabs.com has also been updated accordingly.

AMD’s upcoming desktop Trinity parts are expected to launch in a few weeks and a US retailer has already jumped the gun with some early listings. The listings do not reveal much, but they seem to confirm that Trinity chips will end up on the cheap side.

The pre-order price for the A4-5300 dual-core is $59.60, which sounds fair for a 3.4GHz/3.7GHz part with 1MB of L2 cache and HD 7480D graphics. The black edition A6-5400K comes in at $73.59. It is clocked at 3.6GHz and it can hit 3.8GHz on Turbo and it features beefier HD 7540D graphics. Both dual-core parts are rated at 65W.

In the quad-core world, AMD offers the A8-5500 for $109 and the A8-5600K is also listed at $109. The 5500 is clocked at 3.2GHz/3.7GHz and it has a 65W TDP, while the 5600K runs at 3.6GHz/3.9GHz, but it ends up with a 100W TDP rating. Both have 4MB of cache and HD 7560D graphics.

The A10-5700 and A10-5800K follow the same pattern and both cost $131. The 5700 is a 65W part, clocked at 3.4GHz base and 4.GHz turbo, while the 100-watt 5800K runs at 3.8GHz/4.2GHz. Both have HD 7660D graphics and 4MB of L2 cache.

AMD’s upcoming A10-5800K APU has apparently been put to the test and the benchmarks show mixed results. Of course, we cannot verify any of the results, so take them with a grain of salt.

The new Trinity based quad-core runs at 3.8GHz, but it overclocks to 4.2GHz on Turbo Core. It features 4MB of L3 cache and powerful HD 7660D graphics, all packed in a 100W TDP envelope.

Pitted against the Llano based A8-3850K, the new Trinity core shows superior GPU performance, but the CPU part doesn’t seem too impressive. In 3Dmark 06, Trinity scores 4303, while Llano manages 3814. The advantage widens in SM 2.0 tests, with 3285 marks versus 2139 and in SM 3.0 tests Trinity hits 4067, while the old Llano churns out 2552.

So it is great in GPU intensive tests, but overall it is not too impressive. In Super Pi it is only 12 percent faster than Llano, but Super Pi is not a very comprehensive benchmark.

AMD is expecting Trinity to deliver an overall performance boost of about 30 percent, but as far as we can gather, most of the improvement is down to the new GPU core, not the Bulldozer-derived Piledriver CPU core.

Donanimhaber.com managed to score more details on AMD's upcoming A10-, A8-, A6- and A4- Trinity APUs that will be a part of the Virgo FM2 platform. The specs don't look to shabby and it appears that Trinity will certainly pack a punch with up to 4.2GHz Boost CPU clock, up to 800MHz GPU clock, up to 384 GCN stream processors and all at reasonable 100W TDP.

The full lineup starts with the flagship A10-5800K Black Edition quad-core APU that features HD 7660D graphics, has 4MB of L2 cache, and works at 3.8GHz base and 4.2GHz boost CPU clock. The GPU part of this APU, named HD 7660D features 384 GCN stream processors (or Radeon Cores 2.0, as AMD calls them now) and works at 800MHz. The A10-5800K is closely followed by non-Black Edition A10-5700 quad-core APU that features the same GPU but has slightly lower clocks for both CPU, 3.4GHz/4.0GHz, and GPU part, set at 760MHz. This one, on the other hand, also has a lower 65W TDP.

The A8- Trinity lineup also has two quad-core models, the A8-5600K and the A8-5500. As you can guess from model names, the A8-5600K is a Black Edition part, while A8-5500 will lack that sticker. Both models feature the same HD 7560D GPU clocked at 760MHz with 256 Radeon Cores 2.0. The A8-5600K is a 100W TDP part with 3.6GHz base and 3.9GHz boost CPU clocks while the A8-5500 will have to settle with 3.2GHz and 3.7GHz CPU clock.

The lonely A6-5400K and A4-5300 dual-core Trinity parts will both feature 1MB of L2 cache and the same 65W TDP. The A6-5400K Black Edition packs HD 7540D GPU part with 192 GCN stream processors while the A4-5300 will feature HD 7480D GPU with 128 GCN stream processors. Since dual-core Trinity APUs are scheduled for the Q3 2012, the precise clocks for both GPU and CPU are still unknown.

The A4-5300 is also the only part to support DDR3-1600 memory, while the rest of the lineup will be quite happy with up to DDR3-1866 memory.

Now all we need is to wait for the Q2 of this year in order to see those new Trinity parts in real-world action, but the specs are promising to say the least.